The invention relates generally to a method of image reconstruction in an MR system, and more particularly, to a method of image reconstruction of multi-echo MR data using a probabilistic mathematical expression to generate an MR image having reduced image artifacts.
When a substance such as human tissue is subjected to a uniform magnetic field (polarizing field B0), the individual magnetic moments of the spins in the tissue attempt to align with this polarizing field, but precess about it in random order at their characteristic Larmor frequency. If the substance, or tissue, is subjected to a magnetic field (excitation field B1) which is in the x-y plane and which is near the Larmor frequency, the net aligned moment, or “longitudinal magnetization”, MZ, may be rotated, or “tipped”, into the x-y plane to produce a net transverse magnetic moment Mt. A signal is emitted by the excited spins after the excitation signal B1 is terminated and this signal may be received and processed to form an image.
When utilizing these signals to produce images, magnetic field gradients (Gx, Gy, and Gz) are employed. Typically, the region to be imaged is scanned by a sequence of measurement cycles in which these gradients vary according to the particular localization method being used. The resulting set of received NMR signals are digitized and processed to reconstruct the image using one of many well known reconstruction techniques.
Magnetic resonance (MR) imaging of hyperpolarized substances such as carbon-13 has received interest for a variety of in vivo imaging applications. However, such imaging is subject to a rapid loss of magnetization of the hyperpolarized substances, which may be further affected when multiple substances having different chemical shift are imaged.
One method for imaging the carbon-13 isotopes, for example, uses an echo planar spectroscopic imaging technique that requires the acquisition of large amounts of data. A large amount of data is needed to obtain significant spectral resolution when a Fourier transform is performed on the data to produce a spectrum. However, as a result of the large amount of data that is acquired in order to achieve this spatial resolution, scan times must be increased accordingly, which is undesirable in many imaging scenarios.
It would therefore be desirable to have a system and method capable of reconstructing multi-echo data in a computationally efficient manner to form MR images having few artifacts.